Yes. Marlin is old. Any "new" versions were modified old versions that still suffer from the same compiling issues and poor segment quality. Repetier Firmware is easier to configure, easier to adjust and has a great host interface.

I've made a Delta printer based on uDelta (micro delta). All parts work well, but the Z-axis!! It moves upward, perfectly, but in the reverse direction it has no move and because of other axis moving, the effector move to the non-centered position. So, I couldn't calibrate it yet.